An inner liner excellent in air permeation resistance has been proposed for the purpose of developing fuel-saving and lightweight tires, and for example, tires highly filled with soft carbon black such as GPF, SRF or the like are known, but are problematic in point of flexure failure resistance and low-temperature characteristics in use in cold environments.
Also known are a technique of incorporating flat mica in a rubber composition (see Patent Reference 1), and a blending technique of incorporating a layered or platy clay mineral such as clay or the like in a rubber composition along with incorporating the above-mentioned soft carbon black therein (see Patent References 2 and 3); however, there may be a probability that the flexure failure resistance and the low-temperature characteristics of the rubber compositions may worsen though the air permeation resistance thereof could be enhanced. Accordingly, it is necessary to develop a rubber composition excellent in flexure failure resistance and air permeation resistance for meeting the requirements of the marketplace including weight saving (fuel saving) of tires.